St Louis Pest Control Blog

St. Louis Pest Control – Overwintering Pests

I have just gotten my first sample of some overwintering pests trying to get into someones house.  In this case it was the Box Elder Bug that was all over the outside of their home.   At Blue Chip Pest Services, we deal with these all of the time, here are some facts, pictures, and control strategies for each of these pests.

Now it is a bit early in the season, but these low 50 overnights we have had are messing with the bugs sense of urgency in regards to finding a winter home.  The most common overwintering pests that we encounter are the Ladybug, Cluster Fly, some Wasps, and the Box Elder Bug.  See below for picture of each.


What these pests typically do, is in the fall of each year they will start looking for a home to survive the winter in.  They are typically most attracted to light colored homes, (white / yellow) and will often go to the South or West sides of the home as they receive the most sunlight in the winter months.  Most of these pests are harmless, and are simply trying to stay warm.   It is very likely that even if they invade your home, you may never actually encounter them as they will often go into attic spaces or wall voids, not all the way into the home.  When they are encountered most is in the spring time as temperatures begin to warm.  As the walls heat up, the bugs decide to leave their hiding spot and go back outside, problem is that most are not the good with directions, and some will end up going all the way into the house thinking it is the outside.  Once there, they will head for windows or doors trying to get out, where most will die.  Here is a short paragraph on each of these pests.

Lady Bug:

Brought to the USA as a beneficial pest to eat aphids, these pests are mostly just a nuisance.  They can invade in large numbers and if they get inside may leave marks on walls or windows where they crawl.  If you find them, it is best to vacuum them up and discard them in the trash.  Control of them can only be achieved in the fall before they enter by applying a pest control residual material to the areas that they will try to enter the home such as around windows, doors, and under vinyls siding.

Paper Wasp:

These pests will most often be found trying to live inside of chimneys of homes, or plenum air spaces of businesses.  By the time they make it into the home, they are mostly harmless and are not likely to sting.  The best way to rid yourself of them in the home is to build a fire in the fireplace.  If they are in your office, a fogging application can be made to these plenum air spaces for immediate control.

Box Elder Bug:

These pests which are typically found in conjunction with Box Elder trees (three leaf maple) on or near the property, are again a mostly harmless pest.   They will emerge in the fall as bright red immatures, and from there try to enter the home to again stay warm for the winter.  A residual pest control application in the fall to areas such as windows, doors and under siding around the home will prevent most of their entry inside.

Cluster Fly:

This insect which looks like a much larger and hairier house fly will invade by the thousands to live inside over the winter.  Their presence is usually not know until their spring emergence when they will if inside “cluster” around windows or doors trying to get outside.  A non residual pest control application with pyrethrin is the fastest way to knock them down, or a vacuum to remove them directly.  They do not bite and are basically harmless.

The common theme for all of these pests is a regular pest control application made to the exterior of the home in the late summer and fall months to prevent their entry in the first place.  While sealing cracks and crevices will help, it is impossible to seal all possible entry points into the home.   Our regular pest prevention program treats the exterior of the home on a regular schedule to keep up a barrier year round for these and other pests.

For more information please give us a call at 636-343-7900 or go to for more information or to setup an appointment with one of our experts.


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